Selena Gomez’s announcement that she underwent a kidney transplant surprised and concerned fans last summer. The singer’s best friend and kidney donor Francia Raisa spoke to W magazine about the surgery and revealed that Selena had complications after the procedure was finished.

“Selena did have a complication, too. A few hours after our surgery, I woke up and had a text from her that said, ‘I’m really scared.’ My kidney was very active, and when it turned I broke an artery,” Raisa said. “They had to take her into emergency surgery and get a vein from her leg and build a new artery to keep my kidney in place. She could have died.”

Gomez’s operation was part of ongoing treatment for lupus, which compromises the immune system and vital organs. In October, she expressed her gratitude for Raisa’s life-saving donation.

“My kidneys were shutting down. My mentality was to keep going,” she told the Today show. “[Raisa] lived with me during this interesting time where my kidneys were just done. That was it, and I didn’t want to ask a single person in my life. The thought of asking someone to do that was really difficult for me. She volunteered and did it. And let alone someone wanting to volunteer, it is incredibly difficult to find a match. The fact that she was a match, I mean that’s unbelievable. That’s not real.”

“She went to go get tests, and she came home one day and she was serious,” Raisa said of the day she decided to help her friend. “We all have our moments, so I just let her do her thing, I didn’t ask questions. She was asking me about my day and she grabbed a water bottle out of the fridge and tried to open it and couldn’t. Then she threw it on the floor, and she fell to the floor and started crying. I was like, ‘What is wrong with you?’ She said, ‘I need a new kidney. I don’t know what I’m going to do, the waitlist is seven to 10 years.’ And it just came out of me, and I said, ‘I’ll get tested.’ I called her assistant behind her back to get the information, and that’s how the process started.”

The actress also explained why she and Selena kept the operation under wraps for some time.

“We didn’t want to tell anybody because recovery was very hard for us, and we went through a depression at the time,” Raísa said. “We kind of just wanted to be normal and not have that attention on us. I really left it up to her. I’ve never had anything personal come out about me before. I’ve dated very famous people, and no one knows because I’m very private. I was like, ‘Did you have to be famous?’”